The invention applies, in particular, to transmitting information between a moving vehicle and fixed electronic equipment. A typical application is constituted, for example, by automatic free passage into a closed area subjected to access authorization: e.g. a gate leading to the premises of an organization, a gate for subscribers on a toll road, etc.
In this type of application, transmission must be ensured under good conditions between a miniaturized transmitter/receiver of very low power on board a vehicle and equipment situated in fixed premises.
The frequencies used lie in the range 50 kHz to 150 kHz. It is thus known to make use of a frame whose dimensions are about 1 meter (m) as the antenna system for the fixed equipment for transmission to the on-board equipment, and a winding on a ferrite core for reception from the on-board equipment. The assembly is placed on a platform next to the path where the vehicle must pass through a kind of tunnel.
However, such a system is bulky and gets in the way of any pedestrian traffic, it is not protected against possible accidents, and the electromagnetic coupling between this antenna system and the antenna system on the moving equipment is poor so that the distance between the vehicle and the platform-mounted antenna system must be very small.
The aim of the present invention is to mitigate these drawbacks.